1. Field of the Invention
This invention relates to the performance optimization of integrated circuit (IC) designs, and particularly to a faster, more efficient approach to timing closure for integrated circuit designs containing pipeline logic structures, especially where the logic compositions of said pipelines structures are unrestricted in their definition.
2. Description of Background
Within IBM automated design of integrated circuits generally employs a suite (mix) of IBM design tools and algorithms to simultaneously address the problems of performance optimization and full design wireability, such as those netweight solutions described in US patent of Publication Numbers US20060015836 A1 dated Jan. 19, 2006 and US20060010410 A1 dated Jan. 12, 2006 illustrating improvements which are now included within a tool set called IBM PISCES and used internally by IBM. Such mixtures have proven effective in achieving these goals for a majority of integrated circuit designs and logic configurations. However, certain specific logic connectivity scenarios and physical configurations have not responded well to this methodology approach. This class of special connectivity scenarios forms a set of degenerate cases when standard linear and quadratic algorithms are employed in design optimization. One case in point has been logic pipeline structures. The placement of logic pipelines in response to standard design optimization tools and algorithms has been poor—resulting in timing violations and missed performance objectives.
Before our invention, designers used simple scripts to re-place the failing pipeline logic. Creation of the scripts carried with it an overhead in manpower and design time. More problematic was the fact that this approach was not very effective for complex pipeline structures. These structures, unlike classic latch to latch pipelines, contained functional logic between the latches for at least some portion of the pipeline. In such cases the ineffectiveness of simple scripts forced designers to resort to more manually directed operations. These operations carried a considerable burden in manpower, and had a considerable impact on design closure schedules.